Choosing the right GRP grating comes down to two things: the span between your supports and the load the panel has to carry. This guide explains how to read GRP grating load and span data, sets out the deflection limits to design to, and gives the deflection figures for our standard open mesh panels so you can specify with confidence.
Deflection limits to design to
Deflection is how far a panel flexes under load. For pedestrian areas, a panel should not deflect by more than 10mm or 1/200th of the span, whichever is the smaller, and the difference in level between a loaded and an adjacent unloaded panel should not exceed 4mm. These limits follow BS 4592-0:2006. Keeping within them gives a floor that feels solid and safe underfoot.
How to read the tables
The tables below show how far each panel deflects under a central point load (a 300 x 300mm contact area, similar to pedestrian loading) at four common spans. Find your span, then read across to your load to see the expected deflection. As a rule, a thicker panel or a shorter span deflects less. The mesh figure (for example 32mm) is the open hole size.
Span 457mm
| Panel (thickness / mesh) | 149 kg | 372 kg | 745 kg | 1117 kg | 1490 kg | 2234 kg | 2979 kg |
|---|---|---|---|---|---|---|---|
| 25mm / 32mm | 0.3 | 0.7 | 1.6 | 2.2 | 2.7 | 4.2 | 5.2 |
| 38mm / 32mm | 0.2 | 0.4 | 0.7 | 0.9 | 1.1 | 1.7 | 2.2 |
| 50mm / 42mm | 0.1 | 0.2 | 0.35 | 0.5 | 0.65 | 0.90 | 1.1 |
Span 610mm
| Panel (thickness / mesh) | 149 kg | 372 kg | 745 kg | 1117 kg | 1490 kg | 2234 kg | 2979 kg |
|---|---|---|---|---|---|---|---|
| 25mm / 32mm | 0.7 | 1.7 | 3.2 | 4.6 | 6.1 | 9.1 | 12.1 |
| 38mm / 32mm | 0.35 | 0.9 | 1.5 | 1.9 | 2.4 | 3.5 | 4.2 |
| 50mm / 42mm | 0.1 | 0.35 | 0.7 | 1.1 | 1.5 | 2.0 | 2.5 |
Span 914mm
| Panel (thickness / mesh) | 149 kg | 372 kg | 745 kg | 1117 kg | 1490 kg | 2234 kg | 2979 kg |
|---|---|---|---|---|---|---|---|
| 25mm / 32mm | 1.8 | 4.5 | 8.8 | 13 | 17 | 25 | 32 |
| 38mm / 32mm | 0.6 | 1.5 | 2.9 | 4.1 | 5.4 | 8 | 10.6 |
| 50mm / 42mm | 0.2 | 0.7 | 1.4 | 1.9 | 2.9 | 4.2 | 5.5 |
Span 1219mm
| Panel (thickness / mesh) | 149 kg | 372 kg | 745 kg | 1117 kg | 1490 kg | 2234 kg | 2979 kg |
|---|---|---|---|---|---|---|---|
| 25mm / 32mm | 2.95 | 7.55 | 15 | 21 | 31 | 39 | 49 |
| 38mm / 32mm | 0.9 | 2.4 | 4.7 | 7 | 9.2 | 13.7 | 17.5 |
| 50mm / 42mm | 0.4 | 1 | 2.2 | 3.2 | 4.55 | 6.8 | 9.3 |
Choosing the right panel
For most pedestrian walkways with supports at sensible centres, our 25mm or 38mm standard open mesh grating performs well. Where spans are longer or loads heavier, step up to 50mm grating to keep deflection within limits. Browse the full range in our GRP grating category, or see our load deflection data page for the underlying figures.
These figures are a guide based on a central point load. For project-specific design involving uniformly distributed loads, wheel or trolley loads, or critical applications, contact our team on 01480 570001 or email loadings@gratingdirect.co.uk and we will help you specify the right panel and support centres.
Frequently asked questions
What is the maximum deflection allowed for GRP grating?
For pedestrian areas, deflection should not exceed 10mm or 1/200th of the span, whichever is smaller, with no more than 4mm difference between a loaded and an unloaded panel, in line with BS 4592-0:2006.
Which GRP grating is strongest?
Of our standard open mesh range, 50mm grating deflects the least under a given load and span, so it is the strongest choice for longer spans or heavier loads. 25mm and 38mm suit shorter spans and pedestrian use.
How far can GRP grating span?
It depends on the load and the deflection limit. Use the tables above to check the deflection at your span and load, and reduce the support centres or increase the panel thickness if you exceed the limits.
This guide is for general information. For safety-critical or structural applications, confirm the design with a suitably qualified engineer.
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